Question: Add.
Answer: There are many ways to solve this problem. Let's see two ways we can solve it. Place value table Let's line up the numbers by their decimal places. Tens Ones $.$ Tenths ${8}$ $.$ ${4}$ $1$ $1$ $.$ ${5}$ Now, let's add each place value column. Tens Ones $.$ Tenths ${{8}}$ $.$ ${4}$ $+$ $1$ ${1}$ $.$ ${5}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $1$ $9$ $.$ $9$ Decomposing the numbers We can group the whole numbers together and the decimals together. $\begin{aligned} &({8} + {11}) + ({0.4} + {0.5})\\\\ &={19} + {0.9}\\\\ &=19.9 \end{aligned}$ $19.9 = 8.4 + 11.5$